Figure 5-9: Channel Bandwidth and Transmission Speed study Figure) Signal Bandwidth Chapter 3 discussed a wave operating at a single frequency However, most signals are spread over a range of frequencies The higher the speed, the greater the spread of frequencies Amplitude Signal Frequency 5-16
5-16 Figure 5-9: Channel Bandwidth and Transmission Speed (Study Figure) • Signal Bandwidth – Chapter 3 discussed a wave operating at a single frequency – However, most signals are spread over a range of frequencies – The higher the speed, the greater the spread of frequencies Amplitude Frequency Signal
Figure 5-9: Channel Bandwidth and Transmission Speed study Figure) Channel Bandwidth Higher-speed signals need wider-bandwidth channels Channel bandwidth is the highest frequency in a channel minus the lowest frequency An 88.0 MHz to 88.2 MHz channel has a bandwidth of 0. 2 MHZ (200 kHz) Amplitude 88.0 MHz 88.2 MHz Frequency Bandwidth=0.2 MHz 200 kHz 5-17
5-17 Figure 5-9: Channel Bandwidth and Transmission Speed (Study Figure) • Channel Bandwidth – Higher-speed signals need wider-bandwidth channels – Channel bandwidth is the highest frequency in a channel minus the lowest frequency – An 88.0 MHz to 88.2 MHz channel has a bandwidth of 0.2 MHz (200 kHz) 88.0 MHz 88.2 MHz Bandwidth = 0.2 MHz = 200 kHz Amplitude Frequency
Figure 5-9: Channel Bandwidth and Transmission Speed (Study Figure) Shannon equation Specifies the connection between channel bandwidth and the channel's maximum signal transmission speed -C=B[LOg2 (1+S/N)] C=Maximum possible transmission speed in the channel( bps) B= Bandwidth(Hz) S/N= Signal-to-Noise Ratio Measured as a ratio If given in dB, must convert to ratio 5-18
5-18 Figure 5-9: Channel Bandwidth and Transmission Speed (Study Figure) • Shannon Equation – Specifies the connection between channel bandwidth and the channel’s maximum signal transmission speed – C = B [ Log2 (1+S/N) ] • C = Maximum possible transmission speed in the channel (bps) • B = Bandwidth (Hz) • S/N = Signal-to-Noise Ratio – Measured as a ratio – If given in dB, must convert to ratio
Figure 5-9: Channel Bandwidth and Transmission Speed (study Figure) · Shannon Equation -C=B[Log2(1+S/N) Note that doubling the bandwidth doubles the maximum possible transmission speed Increasing the bandwidth by x increases the maximum possible speed by X Wide bandwidth is the key to fast transmission Increasing S/n helps slightly but usually cannot be done to any significant extent 5-19
5-19 Figure 5-9: Channel Bandwidth and Transmission Speed (Study Figure) • Shannon Equation – C = B [ Log2 (1+S/N) ] • Note that doubling the bandwidth doubles the maximum possible transmission speed • Increasing the bandwidth by X increases the maximum possible speed by X – Wide bandwidth is the key to fast transmission – Increasing S/N helps slightly but usually cannot be done to any significant extent
Figure 5-9: Channel Bandwidth and Transmission Speed (study Figure) Broadband and narrowband Channels Broadband means wide channel bandwidth and therefore high speed Narrowband means narrow channel bandwidth and therefore low speed Narrowband is below 200 kbps Broadband is above 200 kbps 5-20
5-20 Figure 5-9: Channel Bandwidth and Transmission Speed (Study Figure) • Broadband and Narrowband Channels – Broadband means wide channel bandwidth and therefore high speed – Narrowband means narrow channel bandwidth and therefore low speed – Narrowband is below 200 kbps – Broadband is above 200 kbps